On 11-02-13 02:53 PM, Phillip Susi wrote:
On 02/13/2011 01:28 PM, Curtis Gedak wrote:
It might be useful to print a message indicating a problem with invalid
CHS geometry, and that parted will write a geometry when edits are made
to the partition table.
What are your thoughts regarding informing the user about invalid CHS?
CHS is just leftover garbage from the days when dinosaurs walked the
earth. Nobody actually uses it anymore, so it doesn't really matter.
If the existing CHS addresses are nonsense, then parted can hardly
make it any worse, and so no harm will come from it. I therefore
don't see any reason to send the user into a panic warning them about it.
There are some old operating systems, such as DOS, that pay attention to
the CHS values. Today I think DOS is mainly used as a base OS for
programs to re-flash the BIOS on a motherboard. In these types of
situations, I do not think multiple disk partitions are a concern.
Hence you might be right that a warning message might cause more
confusion than it is worth.
TEST B SUMMARY
--------------
Parted also changes the disk geometry to a valid one when a new
partition is created. Now that the CHS geometry has changed, fdisk no
longer sees the original partition as cylinder aligned. I wonder if this
change in geometry could possibly cause problems later on....
There actually isn't anything to change since the disk geometry is not
stored in the partition table. Parted just tries to guess what
geometry was used to compute the existing CHS addresses from their
LBA, and use that same geometry when it needs to compute a CHS
address. If that guess fails, then I believe parted just assumes the
max values for heads and sectors when it has to write CHS values.
I agree that the CHS values are calculated and not actually stored in
the MBR. Hence fdisk must also have some sort of calculation to derive
CHS values for a device. Still, changing of the values would have an
impact on some old operating systems, such as DOS. However as stated
above, I think DOS is mostly used in trivial situations where multiple
disk partitions are not needed. Also DOS would be unable to address all
of the storage space on todays large hard disk devices.
Regards,
Curtis
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